The primary objective of this proposal is to further evaluate the mechanism of lipid alterations following portacaval shunting in the pig. Three approaches are planned following portacaval shunt: 1) evaluation of hepatic cholesterol and lipid synthesis in the Yucatan miniature swine, 2) evaluation of cholesterol degradation, 3) evaluation of the ability of the shunt to reverse atherosclerosis. Portacaval shunt has been shown to be an effective means of lowering cholesterol levels in type IIA hyperlipoproteinemia patients. The physiologic mechanisms of postshunt lipid lowering are still poorly understood. This project is designed to evaluate cholesterol synthesis and degradation following shunt. Our initial studies in the New Zealand white pig have shown that cholesterol synthesis is lowered, and this will be conformed using the Yucatan. Studies of cholesterol degradation following portacaval shunting have not yet been reported. Pigs will be made atherosclerotic by feeding a high fat-high cholesterol diet. Some animals will then be shunted and some will be sham-operated. It is not yet known if portacaval shunt results in reversal of atherosclerosis concomitant with lipid lowering. If this occurs in the atherosclerotic pig, it may also occur in the human.